313D Psychrometrics and Humidity Control 2

Question 1

What does the Sensible Heat Ratio (SHR) of a cooling system represent?

Accepted Answer

The ratio of sensible heat removal to total heat removal (sensible plus latent)

Answer

The ratio of latent heat removal to total heat removal

Answer

The ratio of supply air temperature to return air temperature

Answer

The ratio of indoor humidity to outdoor humidity

Question 2

What happens to relative humidity when air temperature increases while the moisture content stays the same?

Accepted Answer

Relative humidity decreases because warmer air can hold more moisture

Answer

Relative humidity increases because warmer air holds less moisture

Answer

Relative humidity stays constant because no moisture was added or removed

Answer

Relative humidity immediately reaches 100% at elevated temperatures

Question 3

What is the primary function of a humidistat in a residential HVAC system?

Accepted Answer

To sense indoor relative humidity and signal the system to humidify or dehumidify

Answer

To measure refrigerant pressure on the suction line

Answer

To regulate blower motor speed based on duct static pressure

Answer

To measure the temperature differential across the evaporator coil

Question 4

How many grains of moisture are in one pound of water?

Accepted Answer

7,000 grains

Answer

1,000 grains

Answer

5,040 grains

Answer

10,000 grains

Question 5

Under what condition does condensation form on interior window surfaces?

Accepted Answer

When the window surface temperature drops below the dew point of the indoor air

Answer

Whenever indoor relative humidity exceeds 30%

Answer

Whenever indoor relative humidity exceeds 50%

Answer

Only when outdoor temperatures exceed indoor temperatures

Question 6

What does a high latent load in a residential building indicate?

Accepted Answer

There is significant moisture that the cooling system must condense and remove

Answer

The building envelope has insufficient insulation for the climate

Answer

The supply air temperature must be lowered to maintain comfort

Answer

The ductwork is undersized and restricting airflow

Question 7

What is the bypass factor of a cooling coil?

Accepted Answer

The fraction of airflow that passes through the coil without making effective thermal contact

Answer

The ratio of air that bypasses the filter media to total airflow

Answer

The amount of refrigerant bypassed around the expansion valve at part load

Answer

The heat transfer rate through the outer casing of the air handler